692 INTERNAL SECRETIONS AND PRESERVATION OF LIFE. 



take place in cells, and the only available cells in this locality 

 are those which line the intestine, or the leucocytes which 

 wander hetween them. Accordingly, both have been credited 

 with the power of absorbing and transforming these sub- 

 stances." 23 



If our views concerning the functions of the epithelial 

 cells of the intestines, as submitted in the seventh chapter, are 

 sound, they subserve an entirely different function from that 

 now generally ascribed to them: i.e., that of supplying the 

 intestinal tract with a secretion calculated mainly to asepticize 

 the intestinal contents. On the other hand, we showed that 

 the lymph-follicles, including Peyer's patches, supply leuco- 

 cytes, formed in the cytogenic area of the follicles (Flemming's 

 central nodule) to the intestinal cavity through the fenestrated 

 membrane overlying each follicle. As our inquiry did not 

 afford evidence to the effect that all these leucocytes served 

 to insure destruction of pathogenic bacteria, we stated that 

 some of them carried out this function. Indeed, we had good 

 ground for this limitation, for we had already referred to the 

 iron-laden leucocytes observed by Macallum and we were led 

 later on to allude to those charged with the return of bilirubin 

 to the circulation. That the leucocytes supplied to the intes- 

 tinal canal by the cytogenic follicular areas, include some and 

 probably a large proportion whose functions it is to ingest 

 proteids with the iron and bilirubin, then re-enter the intes- 

 tinal wall by way of the villi, is very likely. To the various 

 agencies thus incorporated in the organism can now be added 

 that referred to by Metchnikoff in the sentence: "The presence 

 of peptones in leucocytes which has been so often proved by 

 Hofmeister." While this contributes further evidence to show 

 that our conception of the whole process must be poised upon 

 solid premises, it also suggests that leucocytes ingest proteids, 

 and not peptones, from the intestinal canal, because peptones 

 are the terminal products of the digestion of proteids. 



If leucocytes ingest proteids, these must accumulate in 

 their perinuclear vacuole and find their way into the nuclear 

 canaliculi. These cells being freshly supplied to the intestinal 



All italics are our own. 



